View Compilation Error

0_0_8171883_18534.cpp: In function `int main()':
0_0_8171883_18534.cpp:8: error: `_int64' undeclared (first use this function)
0_0_8171883_18534.cpp:8: error: (Each undeclared identifier is reported only once for each function it appears in.)
0_0_8171883_18534.cpp:8: error: expected `;' before "sum"
0_0_8171883_18534.cpp:9: error: expected `;' before "a"
0_0_8171883_18534.cpp:12: error: `sum' undeclared (first use this function)
0_0_8171883_18534.cpp:13: error: `num' undeclared (first use this function)
0_0_8171883_18534.cpp:16: error: `a' undeclared (first use this function)
0_0_8171883_18534.cpp:20: error: expected `;' before "j"
0_0_8171883_18534.cpp:20: error: `j' undeclared (first use this function)